It is known in the art to form ribbons of neodymium iron boron alloys by a melt spinning process wherein a suitable alloy in molten condition is directed onto a chill surface of a copper wheel spinning at high speed. In European Patent Application No. 0 133 757 published Mar. 6, 1985, this technique is employed in order to prepare an "overquenched" material. The speed that the wheel turns determines the quench rate of the ribbons that are formed thereon and in turn determines the grain characteristics of the ribbons formed. The speed can be varied to produce amorphous ribbons, fine grained ribbons or large grained ribbons. As the speed increases, the grain size of the ribbons decreases. By "overquenching" material the publication means an amorphous or extremely fine crystal structure, generally less than 20 nanometers in the largest direction. The publication discloses that by hot working such amorphous to finely crystalline solid material to produce a plastically deformed body a magnetically anisotropic permanent magnet results. In Example 1 therein, overquenched alloy is placed into a cylindrical cavity of a round die having upper and lower punches. The die and its contents were rapidly heated under argon with an induction coil to a maximum temperature of 750.degree.. The upper punch exerts a pressure of 32,000 psi to produce a hard strong cylinder having full density. While the mass of the resulting cylinder prepared in this example cannot be directly determined, the original alloy utilized in the preparation of the overquenched ribbons is said to be made up of 40 grams of the mixture of elemental materials. Nowhere is there an indication that less than all of this material is employed in the preparation of the cylinder said to have full density.
It has been learned experimentally that the procedure described in the above-mentioned publication is not suitable for preparing permanent magnets having a mass less than 30 grams because as the mass decreases below 30 grams and particularly below 20 grams full density becomes an unrealized goal. Since the purpose of making high energy magnets is to make smaller devices, such as electric motors, it is extremely important to fabricate magnets having not only the desired configuration but a very small size. In automotive use, for example, many small motors are required. Opening and closing windows is one application among many other applications. It is therefore desired to produce smaller devices having the same power as larger devices previously known and to achieve this goal, smaller magnets must be employed. This object is further enhanced by providing a method by which the small mass magnets can be prepared directly without the need of subsequent machining operations.